config.py

主要定义了一些有关l3的一些配置信息的关键字和默认值，同时声明了一些注册配置的函数。

OPTS = [
    cfg.StrOpt('agent_mode', default=constants.L3_AGENT_MODE_LEGACY,
               choices=(constants.L3_AGENT_MODE_DVR,
                        constants.L3_AGENT_MODE_DVR_SNAT,
                        constants.L3_AGENT_MODE_LEGACY),
               help=_("The working mode for the agent. Allowed modes are: "
                      "'legacy' - this preserves the existing behavior "
                      "where the L3 agent is deployed on a centralized "
                      "networking node to provide L3 services like DNAT, "
                      "and SNAT. Use this mode if you do not want to "
                      "adopt DVR. 'dvr' - this mode enables DVR "
                      "functionality and must be used for an L3 agent "
                      "that runs on a compute host. 'dvr_snat' - this "
                      "enables centralized SNAT support in conjunction "
                      "with DVR.  This mode must be used for an L3 agent "
                      "running on a centralized node (or in single-host "
                      "deployments, e.g. devstack)")),
    # 外部网桥默认就是br-ex
    cfg.StrOpt('external_network_bridge', default='br-ex',
               deprecated_for_removal=True,
               help=_("Name of bridge used for external network "
                      "traffic.")),
    # 元数据端口
    cfg.IntOpt('metadata_port',
               default=9697,
               help=_("TCP Port used by Neutron metadata namespace "
                      "proxy.")),
    cfg.IntOpt('send_arp_for_ha',
               default=3,
               help=_("Send this many gratuitous ARPs for HA setup, if "
                      "less than or equal to 0, the feature is disabled")),
    cfg.StrOpt('router_id', default='',
               help=_("If namespaces is disabled, the l3 agent can only"
                      " configure a router that has the matching router "
                      "ID.")),
    cfg.BoolOpt('handle_internal_only_routers',
                default=True,
                help=_("Agent should implement routers with no gateway")),
    cfg.StrOpt('gateway_external_network_id', default='',
               help=_("UUID of external network for routers implemented "
                      "by the agents.")),
    cfg.StrOpt('ipv6_gateway', default='',
               help=_("With IPv6, the network used for the external gateway "
                      "does not need to have an associated subnet, since the "
                      "automatically assigned link-local address (LLA) can "
                      "be used. However, an IPv6 gateway address is needed "
                      "for use as the next-hop for the default route. "
                      "If no IPv6 gateway address is configured here, "
                      "(and only then) the neutron router will be configured "
                      "to get its default route from router advertisements "
                      "(RAs) from the upstream router; in which case the "
                      "upstream router must also be configured to send "
                      "these RAs. "
                      "The ipv6_gateway, when configured, should be the LLA "
                      "of the interface on the upstream router. If a "
                      "next-hop using a global unique address (GUA) is "
                      "desired, it needs to be done via a subnet allocated "
                      "to the network and not through this parameter. ")),
    cfg.StrOpt('prefix_delegation_driver',
               default='dibbler',
               help=_('Driver used for ipv6 prefix delegation. This needs to '
                      'be an entry point defined in the '
                      'neutron.agent.linux.pd_drivers namespace. See '
                      'setup.cfg for entry points included with the neutron '
                      'source.')),
    cfg.BoolOpt('enable_metadata_proxy', default=True,
                help=_("Allow running metadata proxy.")),
    cfg.BoolOpt('router_delete_namespaces', default=True,
                help=_("Delete namespace after removing a router."
                       "This option is deprecated and "
                       "will be removed in a future release."),
                deprecated_for_removal=True),
    cfg.StrOpt('metadata_access_mark',
               default='0x1',
               help=_('Iptables mangle mark used to mark metadata valid '
                      'requests. This mark will be masked with 0xffff so '
                      'that only the lower 16 bits will be used.')),
    cfg.StrOpt('external_ingress_mark',
               default='0x2',
               help=_('Iptables mangle mark used to mark ingress from '
                      'external network. This mark will be masked with '
                      '0xffff so that only the lower 16 bits will be used.')),
]